IDN

Even dumb people have found a way to abbreviate. IDN stands for "I don't no." An educated person says "I don't know," which can be abbreviated to "IDK." If you see someone that types "IDN" on a regular basis, you know that their IQ isn't very high. NOTE: If said person is dumb enough to use IDN, I doubt they'd take the time to use capitals, making it "idn." You may also see "IN", or "in," which can translate into the opposite: "I know," or to an educated abbreviator, "ik. "